1. Field of the Invention
The present invention relates to antimicrobial materials and methods of preparing the same for delivering biocidal agents to wounds. More specifically, the invention relates to hydrophilic/hydrophobic polymer blends that can be used to control the rate of release of silver ions and chlorite ions to a target site such as a wound.
2. Background of the Invention
Skin wounds (e.g., cuts, scraps, lesions, lacerations, burns etc.) often become infected. This can slow or complicate the healing process, and in some instances, prevent healing from occurring. Infection can also increase the costs associated with treating the wound.
Wound dressings have been used to protect the wound from external environments and to reduce the possibility of wound infection. The use of topical antimicrobial agents can be used in conjunction with wound dressings. Antimicrobial agents have also been used in wound dressings.
Chlorine dioxide is a known biocidal agent that can penetrate through both inorganic and organic amorphous material and is effective in killing mold and bacterial spores, viruses and vegetative bacteria. As an oxidizing gas it can penetrate orifices and have biocidal action against difficult to kill bacterial spores even on dry porous substrates (Han et al., 2003). The mechanism of killing by chlorine dioxide has been investigated (Young et al., 2003).
Silver ion is another biocidal agent that can be incorporated in polymer films and fibers. A problem associated with the use of silver ions is that they are sensitive to light which causes discoloration of the silver ion containing material—an aesthetically un-pleasing event. Attempts have been made at creating photo and thermally stabilized silver ion formulations for wound dressing.
U.S. Pat. Nos. 5,326,567, 5,662,913, and 5,744,151 describe stabilizing silver ion in a oligoethylene oxide complex in an environment containing an excess of halide ions. A problem with this technique is that it appears to be suitable for use in solutions only and are sensitive to solvent and salt conditions.
Wound dressings containing silver nanoparticles are highly colored due to the plasmon resonance of the silver particles or have a metallic sheen, especially if the polymer films or fibers are overcoated with continuous metal (Dowsett, 2003; Holder et al., 2003). Silver nanoparticles have been microencapsulated in methyl methacrylate polymer and have shown biocidal activity (Lee et al., 2004).
Light stable compositions with allantoin (U.S. Pat. No. 5,863,548) and carboxymethylcellulose (U.S. Pat. No. 5,709,870) have also been attempted. The use of anionic polysaccharides to stabilize the silver ion are explained in U.S. Pat. Nos. 6,605,751 and 6,669,981. Other controlled release, silver ion based products, are ammonium complexed silver ion (Contree™ by Coloplast) and silver calcium phosphate Arglaes™ (Medline) (Avent et al., 2003) and silver ion infiltrated zeolites (AgION). Crown ethers that selectively bind silver ion have been copolymerized with chitosan (Yi et al., 2003).